Reduction of Self-Quenching in Fluorescent Silica-Coated Silver Nanoparticles

This paper reports the development of spherical Ag@SiO₂ nanocomposites in which fluorescein isothiocyanate molecules have been incorporated using a silane coupling agent and a straightforward microemulsion-based synthesis procedure. The photophysical characteristics of core-shell and coreless nanostructures with similar silica shell thickness and fluorophore densities are measured and compared, and show unequivocally that the presence of the silver core decreases the fluorophore lifetime by a factor as high as 4 and that the steady-state fluorescence intensity is increased by a factor as high as 3. The relationship between the enhancement in fluorescence yield and the influence of the silver core on resonance energy transfer processes was examined by fluorescence lifetime and anisotropy measurements. These Ag@SiO₂ core-shell nanoparticles provide higher detectability and lower self-quenching, whereas the faster recycling time offers more robustness toward photobleaching.